An image formation apparatus includes a conveyance path where a sheet is conveyed, and an image formation unit where an image represented by image data is formed on the sheet conveyed using the conveyance path. As the image formation apparatus operates to convey sheets, paper dust is generated from the sheet.
In order to increase the color reproducibility, some of the image formation apparatuses capable of color printing have a color sensor in the conveyance path, measures the color of a color patch formed on a sheet, and calibrates the color.
The paper dust on the white calibration plate to be measured with the color sensor deteriorates the measurement accuracy. In view of this, the image formation apparatus in which the white reference plate (white calibration plate) is covered with a shutter and the shutter covering the white reference plate is moved to a retraction position when the white reference plate is measured with the color sensor has been suggested (for example, see Patent Literature 1).
This type of color sensor is to measure the color of a sample surface by reflecting the illumination light from a light source on the sample surface, receiving the reflected light with a light reception lens, and analyzing the received reflection light. The light source and the light reception lens are housed in a housing, and the housing has a light passage port serving as both the outlet for the illumination light and the inlet for the reflection light.
In the case of the image formation apparatus where the printing is executed at high speed (for example, a production printer), the paper dust is generated in large quantity. In an aspect conceived in order to prevent the paper dust from covering the light reception lens and the light source, the light passage port is closed with a transparent member such as a transparent glass plate.
In this aspect, however, a large quantity of paper dust adheres to the glass plate and it is therefore necessary to avoid the decrease in colorimetric accuracy because of the paper dust.
Thus, in regard to the colorimetric sensor device used under circumstances where the dust such as the paper dust is generated, the technique to avoid the decrease in colorimetric accuracy has been desired.